12

Subroutines and the Stack

A subroutine is a piece of code that is called from a point within a program and executed, and then a return is made to the instruction after the calling point. All computers use subroutines, but some computers provide a programmer with more facilities to implement subroutines than others.

In this chapter, we will look at the ARM’s subroutine handling mechanisms – in particular, the following:

• The special branch and link instruction
• The stack
• A subroutine call and return
• Block move instructions